Gypsum composition and building construction



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GYPSUM COMPOSITION AND BUILDING CONSTRUCTION 2 Sheets-Sheet 1 OriginalFiled June 2'7, 1960 IN VEN TOR.

3,269,071 GYPSUM COMPOSITION AND BUILDING CONSTRUCTION Original FiledJune 27. 1960 Aug. 30, 1966 s. JOHNSON 2 Sheets-Sheet 2 is T i N. E M WT U 0 D C NS IIFTPIEJ D MY N E G U C A C CL. L T3AS T \J MWN S R Tw N ONE E P RT C C w lf R Afl' P A E LR P T F E E M CETWU EDSLS TP A R P 5 m PWmIUZ 7: 2 OZ. UmJL m D O 5 O 5 O 5 n v 3 2 2 I. M MW 0 o 0 o 0 0 UnitedStates Patent 3,269,071 GYPSUM COMPOSITION AND BUILDING CONSTRUCTIUNElmer S. Johnson, deceased, late of Arlington Heights, Ill., by LucilleG. Johnson, executrix, Arlington Heights, 111., assignor to UnitedStates Gypsum Company, Chicago, 111., a corporation of IllinoisContinuation of application Ser. No. 38,931, June 27, 1960. Thisapplication Sept. 26, 1963, Ser. No. 313,141

3 Claims. (Cl. 52-338) This application is a continuation of co-pendingapplication Serial No. 38,931, filed June 27, 1960, and now abandoned.

This invention relates to new and improved gypsum compositions and topoured monolithic gypsum roof and floor structures made therefrom.

Gypsum has long been utilized in the construction of poured reinforcedroof structures which are fireproof, in sulating and low cost. Roof andfloor structures of this type made from a monolithic gypsum cast placedover sheet-like members resting on spaced parallel supports aredisclosed in US Patent No. 2,233,054.

Poured monolithic roof structures of the type described above andutilizing nonreinforcing aggregates, such as expanded perlite in thegypsum compositions, are also known. One advantage of using light-weightexpanded aggregates, such as perlite and vermiculite, is that superiorinsulating and handling properties are obtained in the production ofcast gypsum objects along with the further advantage of reduced weight.This of course is particularly valuable in roof deck structures,particularly where the structure is used as the ceiling for the floorbelow, or as a flooring base. It may also be appreciated that the use ofsuch aggregates makes the roof structure more lireproof.

One ditficulty that has been observed in the case of lightweightnonreinforcing mineral aggregates, such as expanded perlite or Wood inpoured gypsum roof structures, is the pronounced sagging of the gysurnroof in the area between the parallel supports. Such sagging, of course,causes stresses in the cast gypsum structure and ultimately results incracks.

Accordingly, it is an object of the present invention to provide animproved gypsum composition of superior rigidity.

Another object is the provision of lightweight, low cost monolithic castgypsum roof and floor structures which have reduced saggingcharacteristics.

A further object is the provision of a cast gypsum composition havingimproved rigidity.

A still further object is the provision of a low cost poured gypsum roofstructure that is resistant to cracking.

These and other objects of the present invention may be seen from thefollowing specification, drawing and appended claims.

In one broad form the present invention comprises a dry pulverulentcalcined gypsum plaster mix, containing from 0.25 to about weightpercent Portland cement based upon said calcined gypsum and at leastabout 2 cubic feet of a thermally expanded mineral aggregate per 100pounds of calcined gypsum.

While the propontions of Portland cement are broadly as indicated above,a most preferred range of Portland cement is from about 0.5 to about 2.5weight percent on a dry calcined gypsum basis.

The thermally expanded mineral aggregate may be exemplified by perliteor thermally expanded obsidian rock or a thermally expanded mica, suchas vermiculite, of which perlite is the most preferred species. Broadlythe thermally expanded mineral aggregate should be present in the drymix in an amount of from 2 to 6 cubic feet per Patented August 30, 1966pounds of calcined gypsum and preferably from 2 to 4- cubic feet on thesame basis.

It should be understood that the calcined gypsum referred to herein isthe commercial gypsum product con taining various impurities, although apure calcined gypsum containing 100% calcium sulfate hemihydrate mayalso be used.

A further embodiment of this invention is the case hydrated set gypsumcomposition made from the above described gypsum mix. As may beunderstood, the percentages of the components are adjusted to the extentthat the calcined gypsum (also sometimes hereinafter termed stucco) orcalcium sulfate hemihydrate is converted to the dihydrate or CaSO .:2HO, in the set product. Accordingly, in the cast set gypsum compositionthe Portland cement component may be broadly expressed as being presentin an amount of from 0.20 to 4.2% on a hydrated, set gypsum basis andpreferably from 0.4 to 2.1% on the same basis. Likewise the perlite orequivalent should be present in an amount of from about 1.7 to about 5cubic feet per 100 pounds of hydrated and set gypsum crystals, and inthe most preferred instance from about 1.7 to 3.4 cubic feet per 100pounds of hydrated gypsum.

A monolithic gypsum roof "and floor construction is also contemplated asa further embodiment of this invention, said construction comprising aplurality of bulb-T strips supported in spaced parallel relationpreformed plasterboard or formboard panels marginally supported onopposed strip flanges and spanning the space between the bulb-T strips,a reticulated metal reinforcing mesh overlying said bulb-T strips, and alayer of a set gypsum composition disposed in overlying relation to saidformboards to cover the reinforcing'mesh and strips to provide amonolithic encasement therefor; said gypsum composition comprising a setmatrix of hydrated and set gypsum crystals containing from 0.2 to 4.2%by weight of Portland cement based on said set gypsum and from about 1.7to 5 cubic feet of a thermally expanded mineral aggregate per 100 poundsof set gypsum.

For a more complete understanding of this invention reference should behad to the drawings, wherein:

FIGURE 1 is a fragmentary perspective view, partially in section, of amonolithic roof or floor structure, illustrating one embodiment of thisinvention;

FIG. 2 is a transverse sectional view through the embodirnentillustrated in FIG. 1, taken along the line 22 of FIG. 1;

FIG. 3 is a curve illustrating the effect of Portland cement on thegypsum-perlite cast objects.

Referring to the drawing in detail, the embodiment illustrated comprisesa roof or floor construction 4 supported on purlins 6 which may be ofany suitable type, such as an I-beam as illustrated, or the like.Special steel bulb-T strips 8 are transversely supported on the purlins6 in substantially parallel and spaced relation. If desired the bulb-Tstrips 8 may be affixed to the purlins 6 by means of welding or clips(not shown).

The bulb-T strips 8 comprise a base 10 forming wide flanges 12 whichextend laterally from a central vertical web 14. The web 14 terminatesin a so-called bulb portion 16 which may be of any suitable shape, butis preferably substantially rectangular, as shown. The bulb-T strip isprovided adjacent the intersection of the base and web with fillet-likeportions or ribs 18, the outer edge thereof forming elongated shoulders20 running longitudinally along the entire length of the bulb-T strip.

In the embodiment illustrated, a reticulated open metal reinforcing mesh22 is shown suspended overlying the bulbs 16 of the bulb-T strips8.

Plasterboard formboards 24 are illustrated spanning the spaces betweenthe bulb-T strips and supported at their marginal edge portions 26 bythe flanges 12 of the bulb-T strips. These formboards are, asillustrated, plasterboard having a central core 28 of set gypsum orother material encased in paper cover sheets 30. A gypsum composition 32is poured over the structure formed by the bulb-T strips, formboards andreticulated metal reinforcing means to form a uniform monolithicencasement, substantially as illustrated. Formboards other thanplasterboard may also be used, such as formboards made fromdisintegrated wood, such as fiberboard or ceramic fibers, such as blownor drawn glass or mineral wool.

The upper surface 34 of the illustrated floor or roof construction maybe utilized as a base for a roofing material or a flooring structure.

In FIG. 3 the curve illustrates the deflection in inches of gypsum castscontaining 3 cubic feet of perlite per 100 pounds dry gypsum and variousamounts of Portland cement (on a dry gypsum basis). The deflection ininches of a cast bar 2 x 3 inches, 32 inches long, is shown. Thesupports are spaced at 30 inches. The test was run at 90% relativehumidity.

A typical gypsum composition of the type contemplated herein comprisesthe following dry ingredients:

Expanded perlite, cu. ft. 60

Calcined gypsum, lbs. 2,000

Portland cement, lbs.

Retarder (commercial), as required to give the desired set time.

Commercial retarder is well known in the industry and one type isprepared by treating a keratinaceous material with an alkaline solutionand adding a carrier so that the material is a dry powder. Usually notmore than 6 ounces per ton of gypsum is required.

The above dry mix is formed into a slurry by the addition of water, andthe slurry is then poured upon the roof structure as described above,forming a substantially fiat deck or upper surface. The set time incommercial operation is usually from to about 35 minutes. As indicatedabove, the resulting structure is unusually resistant to sagging andconcomitant cracking.

The following table will illustrate the beneficial effect of theincorporation of small amounts of Portland cement in gypsum-mineralaggregate compositions:

From the foregoing examples it may be observed that the sagging ofgypsum-perlite set plaster casts is very markedly reduced by theaddition of small amounts of Portland cement. Note that up to a certainpoint, which is close to 1%, an increase in the percentage of Portlandcement gives a decrease or improvement in the deflection. This is shownin FIG. 3 of the drawings. Note also that excellent results wereobtained when the Portland cement was substantially hydrated to amoisture content of about 7.7%, estimated to be about hydration. Theparticular hydrated Portland cement utilized in the foregoing table wasprepared by mixing Portland cement (100 parts) with water (50 parts) andheating the slurry formed in a water bath (ca. 212 F.) for 46 hours. Theproduct was stored in a sealed container for 3 days, dried at 110 F. toconstant weight and then ground.

A marked decrease in sagging is also obtained when the Portland cementis added to a mix containing expanded vermiculite as well as expandedperlite.

It should be understood that the consistency of the mix may vary;consistency is understood to mean the quantity of water in cubiccentimeters added to the dry gypsum composition. Thus the consistencymay vary from to 140 cubic centimeters of water per 100 grams of gypsummix. Of course, ratio may be expressed in other terms. The improvementsobtained by the addition of Portland cement are observable, however, atcomparable consistencies of the various compositions.

While broadly the amount of Portland cement utilized has been indicatedas from 0.25 to 5.0% (dry calcined gypsum basis) it should be understoodthat the most preferred range is from 0.5 to 2.5% on the same basis,since it has been found that superior wet bonding between the gypsumcomposition and the formboards, when the latter are gypsumplasterboards, is obtained at this level as compared to higher amountsof Portland cement, as well as resulting in minimum sagging.

What is claimed in:

1. An improved lightweight monolithic poured gypsum roof and floorconstruction having a plurality of spaced roof and floor supportingmeans having a vertical web portion and subtending flanges, formboardsdisposed between said supporting means and supported at their marginalportions by the said subtending flanges, an open reticulated reinforcingmeans overlying said supporting TABLE I Percent Consistency Wet 1 hr.Wet sagging 2 Aggregate Type Amount/100 Portland cc. water/100 Densitycompressive inches lbs. plaster l Ccment gins. gypsum lbs/ L strength,15 days plaster lbs./in.

Expanded Perlite O 120 73. 2 243 670 Do 1. 0 130 71. 6 215 .135 Do 0 72.4 393 229 Do 0 120 70. 0 204 632 Do O. 5 71. 0 423 057 Do 0.5 71. 0 352068 Do 0.5 69. 0 251 113 D0- 0. 5 69. 0 216 D0- 0. 5 140 190 210 Do 1.0105 G9. 7 352 .044 Do 1.0 120 68. 7 257 095 Do 1.0 69.1 206 .125 Do 1.0140 68. 5 191 .124 Do 3 1. 0 105 70. 5 246 .058 D0- 3 l. 0 140 68. 7 168102 D0 2. 5 140 69. 5 153 D0- 5.0 140 70.0 126 353 Do 0 125 G3. 4 138 1.705 Do o. 1. 0 180 65.7 108 059 Expanded vermiculite, 3 cu. ft.. 0 10077. 5 156 2. 988 Do .do 1.0 110 75. 5 196 559 1 Dry calcined gypsumbasis.

2 sagging is based upon 2 high x 3 wide x 32" long bars and placed,without drying, on supports 30 apart, immediately after setting, for 15days in an atmosphere of high humidity at room temperature, whichaveraged about 70 F. The specimens were enclosed in a large plastic bagwith a pan of Water underneath the specimens to maintain close to amoisture saturated atmosphere surrounding the specimens.

3 Hydrated,

means and formboards and spanning the spaces between the verticalportions of the supporting means, and a set gypsum overlying theformboards and encasing the reinforcing means and vertical portions ofthe supporting means to encase the same and bonded thereto in amonolithic structure, the set gypsum composition being comprised of anadmixture of water and a dry gypsum mix consisting essentially ofcalcined gypsum, from 0.25 to 5.0 weight percent Portland cement on acalcined gypsum basis and from 2 to 6 cubic feet of perlite aggregateper 100 pounds of calcined gypsum, said admixture forming a gypsumslurry further characterized in having a set time of up to about 35minutes.

2. A roof and floor construction according to claim 1 wherein thePortland cement is present in an amount of from 0.5 to 25 weightpercent.

3. A roof and floor construction according to claim 1 wherein theperlite aggregate is present in an amount of from 2 to 4 cubic feet per100 pounds of calcined gypsum.

References Cited by the Examiner UNITED STATES PATENTS 1,923,370 8/1933Hansen 106-89 2,174,581 10/1939 Hoge 52-338 2,212,811 8/1940 Hann 106-892,233,054 2/1941 Heeren 52-338 2,377,491 6/1945 Goodrich et al. 106-862,406,757 9/1946 Gardener 106-110 2,501,699 3/1950 Stecker -1 252-3782,715,583 8/1955 Ziegler 106-110 FRANK L. ABBOTT, Primary Examiner.

HENRY C. SUTHERLAND, JACOB L. NACKENOFF,

Examiners.

J. L. RIDGILL, Assistant Examiner.

1. AN IMPROVED LIGHTWEIGHT MONOLITHIC POURED GYPSUM ROOF AND FLOORCONSTRUCTION HAVING A PLURALITY OF SPACED ROOF AND FLOOR SUPPORTINGMEANS HAVING A VERTICAL WEB PORTION AND SUBTENDING FLANGES, FORMBOARDSDISPOSED BETWEEN SAID SUPPORTING MEANS AND SUPPORTED AT THEIR MARGINALPORTIONS BY THE SAID SUBTENDING FLANGES, AN OPEN RETICULATED REINFORCINGMEANS OVERLYING SAID SUPPORTING MEANS AND FORMBOARDS AND SPANNING THESPACES BETWEEN THE VERTICAL PORTIONS OF THE SUPPORTING MEANS, AND A SETGYPSUM OVERLYING THE FORMBOARDS AND ENCASTING THE REINFORCING MEANS ANDVERTICAL PORTIONS OF THE SUPPORTING MEANS TO ENCASE THE SAME AND BONDEDTHERETO IN A MONOLITHIC STRUCTURE, THE SET GYPSUM COMPOSITION BEINGCOMPRISED OF AN ADMIXTURE OF WATER AND A DRY GYPSUM MIX CONSISTINGESSENTIALLY OF CALCINED GYPSUM, FROM 0.25 TO 5.0 WEIGHT PERCENT PORTLANDCEMENT ON A CALCINED GYPSUM BASIS AND FROM 2 TO 6 CUBIC FEET OF PERLITEAGGREGATE PER 100 POUNDS OF CALCINED GYPSUM, SAID ADMIXTURE FORMING AGYPSUM SLURRY FURTHER CHARACTERIZED IN HAVING A SET TIME OF UP TO ABOUT35 MINUTES.